Transport of natural soil nanoparticles in saturated porous media: effects of pH and ionic strength

Figures & data

Table 1. Variation of concentration and physicochemical properties soil nanoparticle suspension with soil type in pH 6, IS = 0.01 M.

Property	AS	CS	MS	RS
Concentration (mg L^−1)	524	468	358	465
Particle size (nm)	102	97	54	65
Organic matter (mg g^−1)	2.3	1.0	13.5	8.2

Table 2. Variation in the particle size of soil nanoparticle suspensions with pH 6, IS changing and IS = 0.01 M, pH changing (unit: nm).

Factors	AS	CS	MS	RS
pH 4	110	104	77	80
pH 6	102	97	54	65
pH 8	90	78	50	57
IS = 0.001	95	79	48	63
IS = 0.01	109	93	59	68
IS = 0.1	213	167	176	149

Table 3. Variation in the zeta potential of soil nanoparticle suspensions with pH 6, IS changing and IS = 0.01 M, pH changing (unit: mv).

Factors	AS	CS	MS	RS	Sand
pH 4	−16.2	−12.1	−37.7	−18.2	−13.8
pH 6	−38.1	−26.3	−40.6	−40.9	−24.7
pH 8	−43.9	−18.3	−35.4	−47.5	−29.1
IS = 0.001	−41.1	−30.5	−26.2	−44.1	−27.8
IS = 0.01	−31.2	−25.5	−30.9	−34.2	−23.3
IS = 0.1	−26.3	−20.6	−21.3	−23.1	−15.1

Figure 1. The AFM images of different NS: (a) AS, (b) MS, (c) CS, (d) RS.

Figure 2. Particle size volume of NS used a Laser Particle Sizer.

Figure 3. XRD spectra of different NS.

Figure 4. DLVO energy between NS and sand under three different pH and ionic strength conditions. The primary energy barriers for NS and sand (a) and the secondary energy minimum for NS and sand (b).

Figure 5. The effect of pH on the transport of NS ((a) AS, (b) RS, (c) CS, (d) MS) in saturated porous media.

Figure 6. The effect of ionic strength on the transport of NS ((a) AS, (b) RS, (c) CS, (d) MS) in saturated porous media.

Table 4. Best-fit parameter values and recovery rate calculation for soil nanoparticles with varied pH in IS 0.01 mol L⁻¹.

NS	pH	k(s^−1)	R^2	Recovery rate (%)
AS	4	8.12 × 10^−3	0.96	69.75
	6	5.51 × 10^−3	0.98	79.86
	8	2.81 × 10^−3	0.97	91.02
RS	4	1.63 × 10^−2	0.94	46.45
	6	1.09 × 10^−2	0.98	70.46
	8	8.02 × 10^−3	0.97	36.62
CS	4	2.21 × 10^−2	0.97	38.62
	6	1.40 × 10^−2	0.94	53.82
	8	2.04 × 10^−2	0.91	36.67
MS	4	1.48 × 10^−2	0.84	51.99
	6	1.04 × 10^−2	0.97	62.88
	8	1.60 × 10^−2	0.96	48.73

Table 5. Best-fit parameter values and recovery rate calculation for soil nanoparticles with varied IS in pH 6.

NS	IS (mol L^−1)	k(s^−1)	R^2	Recovery rate (%)
AS	0.001	2.46 × 10^−3	0.99	90.26
	0.01	2.60 × 10^−2	0.93	29.73
	0.1	6.65 × 10^−2	0.45	6.05
RS	0.001	1.28 × 10^−2	0.87	54.36
	0.01	3.18 × 10^−2	0.68	24.3
	0.1	5.11 × 10^−2	0.78	11.29
CS	0.001	1.46 × 10^−2	0.95	52.72
	0.01	1.63 × 10^−2	0.63	18.52
	0.1	6.69 × 10^−2	0.54	6.08
MS	0.001	1.51 × 10^−2	0.96	51.04
	0.01	4.76 × 10^−3	0.96	79.22
	0.1	2.32 × 10^−2	0.53	36.24